Let’s Get Moving!
The fact that you’re reading this means you have a working solarengine (or you’re bored and
just filling time until the TV commercials pass to the next program). This section is designed to
help you get something moving across your desk/floor/sibling/significant other. All the following
locomotion ideas are well tested in existing BEAM machines, with some working better than
others in different situations. We suggest that you try the SYMET idea first as it is simple and
effective, but do try the others for comparison. And don’t hesitate trying to combine them.
“SYMET" Direct Drive
By placing the motor on its face and tilting it just a little, it will
move in one direction. Watch a toy top roll to a stop, and you’ll
recognize the motion in the SYMET drive. The term "SYMET"
comes from "symmetrical", which is useful for robots that reverse
direction when they bump into something. See if you can come
up with a method of making the robot tilt from one side to the
other so it changes direction. This system is simple and
effective, but also results in robots that don’t usually go very
straight - ok for photovores, but bad for solarollers.
Friction Drive
By removing the pulley and placing the shaft of the motor right
up against a wheel, you can motivate your BEAMbot with a
friction system. This arrangement results in straighter-travelling
BEAM critters, but reversing direction becomes a problem.
Slippage between the shaft and the wheel becomes a concern,
which can be fixed by increasing the force between the motor &
wheel, or increasing the friction between the two with some
heat-shrink electrical insulation on the motor shaft.
Pulley Drive
This is what your average cassette deck uses, so you should
have the parts readily available. You usually can cut the pulley
drive right out of the system, motor included. If not, build your
own, making sure to use the black belt from the cassette
mechanism. Elastic bands stretch too much, and why not use
the belt that’s
designed
for this purpose? Be careful not to
make the belt too tight - you’ll simply be wasting power.
Gear Drive
Most battery-powered devices have a gear-drive
somewhere in them but it’s often tough to find gears that
match your motors and wheels. Rip a few things apart and
you may get lucky. Try salvaging the whole geartrain
instead of just prying the gears loose -it’ll work better than
trying to rebuild them yourself. Good places to start looking
are in auto-reverse tape players and clock mechanisms.
Shaft
Rotation
Shaft
Rotation
Travel
Direction
Travel
Direction
Direction of travel depends on which edge of
the pulley touches the surface.
Mount the motor so it
touches the
wheel. A little heat-shrink tubing on the
motor shaft/pulley reduces slippage.
just
Wheel
Motor
Pulley
Belt
Motor
Make double-use of the belt by making
act as a tire as i
i
t
t
goes around the
pulley.
Motor
“Driver” gears
“Driven” gears
Wheel
Arranging gears from
small “driver” gears to larger
“driven” gears increases drive
strength & torque, but decreases
rotational speed.
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